Certainly, one advance will be the main effort, but if that line of advance meets resistance and a secondary advance meets success, your plan should allow the diversion of resources to exploit the new main effort while the original main effort becomes a supporting one. The objective is the same in either case. This is called "reinforcing success."
So how does al Qaeda measure up to this standard of waging war?
The Weekly Standard brings up an interesting bit of information that may relate to this:
Amidst the reporting on the Amman bombings, the Associated Press noted this anecdote with regard to the Radisson SAS hotel, one of the buildings targeted by the suicide bombers: "U.S. officials believe al-Zarqawi and bin Laden operations chief Abu Zubaydah were chief organizers of a foiled plot to bomb the Radisson SAS. The attack was to take place during millennium celebrations, but Jordanian authorities stopped it in late 1999." If this is the case, then the bombing of the Radisson SAS and the two other Amman hotels last week should not be seen so much as an outgrowth of the Iraqi insurgency as much as a tell-tale al Qaeda modus operandi: continuing to target a given location until the attack is carried out successfully (recall the 1993 World Trade Center bombing).
So al Qaeda keeps going after a target until they finally hit it? Even if it takes years? What does this tell us?
Well, it looks like al Qaeda does not reinforce success, but instead blunders headlong into targets that avoided being hit the first time. If their objective is to expel America from the Middle East by hurting us enough to retreat, it doesn't really matter what al Qaeda hits as long as they keep hitting us. This would mean real amateur hour in al Qaeda's ability to wage their war. So please, please, stop telling me how we've fallen into bin Laden's deeply clever trap by waxing his butt all over the world with a global counter-offensive. We and our allies have left the gangly murderer crouched in some cave in North Whositstan without even a decent recording studio to shake his fist at us on a regular basis.
Or it means that the al Qaeda leadership confuses objectives with means. You want to focus on achieving the objective while being flexible on means. Instead, al Qaeda has been flexible on objectives (which varies from getting US troops out of Saudi Arabia, or fighting to defend Afghanistan, or fighting in Iraq to drive us out, or defending the Palestinians, or--what day is it anyway?) while focusing on specific attacks ruthlessly until they hit it. This focus continues regardless of the objective. Does hitting the Jordanian hotel in 1999 really support the same goal as hitting it this year? The same can be said of the World Trade Center in 1993 and 2001.
Finally, it may mean that al Qaeda's resources are so thin that they can't afford to discard intelligence, planning, and deployed resources if the first effort fails. To al Qaeda, even a plot that is discovered cannot be cancelled despite the fact that the target should be more prepared for the next strike. In a perfect jihadi world, you'd switch to a new target that is not aware of your intentions to strike it. Since breaking our morale is the apparent goal for whatever objective they have, if you can afford it you switch to an easier target. But they continue frontal assaults right up the middle.
Really, these guys are amateurs and fantacists. Sadly, they are also stone cold killers, so we must hunt them down and kill them. And we should also focus resources on any target the enemy focuses on even after we foil the first attempt. They may not have a Plan B.
